The present invention generally relates to a connecting structure of an electrical supply bus and, more particularly, to a connecting structure of an electrical supply bus for use in an electronic device such as a computer system.
Hitherto, electrical supply buses of this kind have been used as paths for supplying electric power to printed circuit boards of a computer system, as described in Japanese Unexamined Patent Publication (JP-A) No. 148493/1980 official Gazette (hereunder referred to as a first Official Gazette) or No. 28134/1980 official Gazette (hereunder referred to as a second official Gazette).
In the case of the electrical supply bus disclosed in the first Official Gazette, the electrical supply bus is connected to a power supply module or a logic package by using screws.
Namely, there has been devised a method by which a connecting portion of an electrical supply bus is placed at the rear side of a logic package and by which the electrical supply bus is connected to the logic package by tightening screws from the outside of a case after the logic package is inserted into the case.
In the case of another method employing the electrical supply bus disclosed in the second Official Gazette, coil springs are used at the rear side of a logic package. The electrical supply bus is pressed against the logic package by utilizing the pressure of the coil springs. Thus, the electrical supply bus is connected to the logic package.
The aforementioned two methods are examples of a method of connecting an electrical supply bus to the rear side of a card.
Another example of a conventional method is to insert an electrical supply bus 10, which is attached to a power supply module or a logic package 27, into a case 25 along guide rails 26 thereof and to then connect the electrical supply bus 10 to the guide rails 26 at a plurality of places on the contact surface between the bus 10 and each of the rails 26, as illustrated in perspective diagrams of FIGS. 1A and 1B.
FIG. 2 illustrates the conventional method of connecting the electrical supply bus to the guide rails at the plurality of places on the contact surface between the bus and each of the rails, and is an exploded perspective diagram showing an enlarged view of a connecting portion of the electrical supply bus, namely, a connecting portion between the bus and one of the rails.
Generally, the guide rails 19 are attached to the case 25, and the electrical supply bus 10 is attached to the power supply module or the logic package 27.
In the case of this example of the conventional method, screw holes 21 are formed in the guide rail 19 at a plurality of places. Screws 20 can be inserted into these holes from above, respectively.
Next, an operation of the conventional connecting structure of the electrical supply bus illustrated in FIG. 2 will be described hereinbelow.
FIG. 3 is a sectional diagram showing the connecting state of the electrical supply bus, which is taken on line E--E of FIG. 2. After the electrical supply bus 10 is inserted into the case along the guide rails 19, each of the screws 20 is tightened from the corresponding one of the screw holes 21. Thus, the tip end portion of each of the screws 20 pushes down the electrical supply bus 10 against the lower portion of the guide rail 19.
The electrical supply bus 10 is connected to each of the guide rails 19 by utilizing the forces of these screws 20.
FIG. 4 is a perspective diagram illustrating a structure for performing another conventional method of connecting the electrical supply bus to the guide rails at the plurality of places on the contact surface between the bus and each of the rails.
Further, FIG. 5 is a sectional diagram showing the connecting state of the electrical supply bus, which is taken on line F--F of FIG. 4. This conventional structure uses many connector contacts 23 for connecting the electric supply bus to the guide rails. The connector contacts 23 are placed in two rows or lines on both sides of the guide rail 22, respectively, so that the electrical supply bus 10 is sandwiched between the two rows of the connector contacts 23.
Next, an operation of the conventional structure illustrated in FIGS. 4 and 5 will be described hereinbelow.
When the electrical supply bus 10 is inserted onto the guide rails 22, the interval between the two lines of the connector contacts 23 increases. Then, the electrical supply bus 10 is connected to the guide rail 22 by utilizing the spring force generated in the connector contacts 23 at that time.
Additionally, there has been provided another example of the structure, which is provided with a mechanism 24 for connecting the electrical supply bus 10 to the guide rail 22 by preliminarily increasing the interval between the two rows of the connector contacts 23 when the electrical supply bus 10 is inserted thereonto, and by then narrowing the interval therebetween after the electrical supply bus 10 is inserted thereonto.
The aforementioned conventional structures, however, have the following problems.
First problem is that, in the structure using the screws for fixing the electrical supply bus which has been described as the example of the conventional method, it is difficult to tighten the screws for fixing the electrical supply bus onto the guide rails after the power supply module or the logic package is inserted into the case.
The reason is that the guide rails are mounted in the inside of the case. Thus, the screws for fixing the electrical supply bus should be tightened in the inside of the case. Especially, it is very difficult to tighten screws in an inner part, which does not allow a worker' hands to have access thereto, of the case.
Furthermore, there has been an example of a connecting structure in which a fixing-screw tightening portion of an electrical supply bus is placed at the rear side of a logic package and in which thus, screws for fixing the electrical supply bus are tightened from the outside of a case after the logic package is inserted into the case, similarly as the case of the connecting structure of the electrical supply bus described in the first Official Gazette. In the case of this example, although a connecting operation is simplified, only two places, at which the fixing screws are tightened, are assured for a single logic package. Therefore, the structure has too few connection places or points to supply a large or heavy current that is necessary for an operation of an apparatus such as a current large scale computer.
Second problem is that an operation of connecting the electrical supply bus is troublesome and time-consuming in the case of the connecting structure using the screws for fixing the electrical supply bus, which has been described as the conventional structure.
The reason is that a plurality of screws distributedly or dispersedly arranged on the guide rails should be individually tightened in the case of the hereinabove mentioned structure.
Third problem is that, in the case of the aforementioned conventional structure for connecting the electrical supply bus to the guide rails by using many connector contacts provided therein, a large force is needed when connecting the electrical supply bus.
The reason is that an inserting force increases at the time of inserting the electrical supply bus onto the guide rails as a result of connecting the bus thereto by utilizing the elasticity of may connector contacts in the aforementioned conventional structure.
Further, the problem of the inserting force is solved by the structure provided with a mechanism by which the electrical supply bus is connected to the guide rail by preliminarily increasing the interval between the two rows of the connector contacts when the electrical supply bus is inserted thereonto, and by then narrowing the interval therebetween after the electrical supply bus is inserted thereonto. However, the number of components increases with the result that the cost thereof rises.
Fourth problem is that it is difficult to ensure high reliability in the case of employing the structures which have been described as the conventional structures and which are adapted to connect the electrical supply bus to the power supply module and so on by using the coil springs and the many connector contacts.
The reason is that it is difficult to assure a contact pressure for a long time owing to the presence of a limit to the elasticity of the spring coils and the many connector contacts.